The invention concerns an electric suspension conveyor with
a) a running rail system forming a line network;
b) a plurality of carriages, each having:
ba) at least one travelling mechanism which runs in the running rail system;
bb) at least one load carrier which hangs down from the travelling mechanism;
bc) at least one drive motor;
bd) an autonomous carriage control which, in turn, comprises:
bda) a processor;
bdb) a memory in which can be stored the entire line network and the maximum permissible speed at each location of the line network and the minimum permissible distance from the preceding carriage;
bdc) a controller, driven by the processor, which energizes the drive motor;
c) a central control which assigns the travel tasks to the individual carriages and clears the travel paths in the line network;
d) a code rail system which extends along the line network and carries a code, which can be read out by each carriage, for the position at which the respective carriage is located;
e) a databus rail system which extends along the line network and via which the carriages communicate with one another and with the central control,
f) the carriage control of each carriage requesting from the code rail system, during travel, the respective location of the carriage, obtaining from the memory the maximum speed for this location of the line network and, in the absence of other information, attempting to bring the carriage to the maximum speed.
In known electric suspension conveyors of this type, the autonomous carriage control of each carriage in the entire system attempted to bring the carriage to the maximum speed permissible at the respective position at which the carriage is located. The movement of several carriages in the line network was correlated in that a minimum distance from a preceding carriage was predefined and each respectively following carriage reduced its speed so that this minimum distance could be maintained. Otherwise, the individual carriages moved freely and independently of one another in the line network, according to the commands of the central control.
In the case of this type of operation of the electric suspension conveyor, it was necessary for relatively large safety distances to be maintained between the individual carriages. This means substantial losses of capacity in cases where high travel speeds are sought for the carriages.
The object of the present invention is to develop an electric suspension conveyor of the initially stated type in such a way that its capacity is increased.
This object is achieved, according to the invention, in that
g) the central control either operates each carriage in an individual travel mode or, in a group mode, combines several carriages, traversing certain distances of the line network one behind the other, to form groups in which all carriages have essentially the same speed, and can transmit information on the membership of the group to the individual carriages;
h) the carriage control of each carriage in group mode respectively requests from the code rail system, during travel, the respective location of the carriage, exchanges information, via the databus rail system, on the instantaneously permissible speed of each carriage in the group, and drives the drive motor of the corresponding carriage so that the carriage travels at the lowest permissible speed of all carriages in the group.
Thus, according to the invention, carriages which are intended to traverse certain sections of the line network together and one behind the other are combined to form so-called xe2x80x9cgroupsxe2x80x9d. A group is characterized in that all carriages belonging to it move at the same speed. However, the maintenance of this speed by each carriage is not the result of control processes and distance measurements, which would occupy an excessively long period of time. Instead, each carriage is informed, via the databus system, by all other carriages in the group which maximum permissible speed must be maintained by the other carriages of the group. If even only one carriage in the group signals that at its location it is necessary to maintain a speed which is lower than the hitherto commonly travelled speed, then it is not only that carriage which reduces its speed to the lower permissible value but, rather, all other carriages in the group follow it without a time delay and, in so doing, override the higher speed value that is actually permissible according to the position at which they are located. This adaptation of the speeds of all carriages in the group to the respectively lowest permissible speed, without any appreciable time delay, increases the operational safety.
The greater rapidity in the adaptation of the speeds of the carriages in the group to the uniform, lowest permissible speed enables the minimum permissible distance between the carriages which are operated in group mode to be less than the minimum permissible distance between the carriages which are operated in individual travel mode. Parameters being otherwise the same, a lesser minimum distance between the carriages means an increased conveying capacity.
Alternatively, or additionally, it is possible, in the case of the present invention, for the local permissible speed to be higher for each carriage which is operated in group mode, at least in regions of the line network, than for the carriages which are operated in individual travel mode. Again, parameters being otherwise the same, this means an increased conveying capacity of the overall system.
In a further advantageous development of the invention, each carriage has a distance sensor which ascertains the distance from the preceding carriage and emits a signal to the respective carriage control if a certain minimum distance is not maintained. This distance sensor performs a safety function only, since it has to operate only if the autonomous control of the carriages via the code rail system and the databus rail system should fail for any reason.